Figure 11.

Effects of Ca²⁺_o, Ba²⁺_o, and Mg²⁺_o on gating. (A and B) Chord conductances; (C and D) channel activation. Activation was measured as the relative channel open probability (P_O,r) from the I-V/IIV ratio, normalized (see Materials and methods). Smooth curves in C and D are fits to fourth power Boltzmann relationships. (E and F) Shifts in activation with Ca²⁺_o or Ba²⁺_o (E) and Mg²⁺_o (F). Data are from Fig. S8 A (Ca²⁺_o and Ba²⁺_o) and Fig. S16 A (Mg²⁺_o), except that voltage shifts in Ba²⁺_o are defined with respect to 2 mM Ba²⁺_o (not 2 mM Ca²⁺_o). The smooth curve is the fit to Gouy-Chapman theory with a single uniform surface charge density (see Materials and methods).